Smokeless fire pit

ABSTRACT

A combustion device includes a combustion chamber with an outer wall enclosing a combustion space that can contain a fuel source on an adjustable fuel rack, side walls, a lower air jet tube and at least one air upper jet tube, a top opening, a grill top assembly to cover the opening, and a detachable power module. The power module can have batteries and a blower. The blower can force ambient air into a manifold, through the jet tubes, through ports in the jet tubes, and into the combustion chamber.

FIELD OF THE INVENTION

The present invention relates in general to outdoor heating equipmentand in particular, relates to a fire pit that is smokeless.

BACKGROUND OF THE INVENTION

Fire pits are a source of combustion that gives off thermal energy asheat for warmth and cooking, as well as providing a social gatheringplace. Fire pits are a contained place for inserting fuel for combustion(for example, wooden logs and kindling). By way of example, fire pitscan be a simple depression in the earth, a raised rock linedconstruction, or a raised ceramic and/or metal housing with legs.Combustion produces smoke, and even in the lightest of airs, the firewill draw air past the people sitting about the fire pit. This movementof airs can create small vortices, or personal eddies, around the peoplesurrounding the fire pit. Combustion gases, such as smoke, can be drawntowards these eddies when winds shift, creating the impression to mosteveryone seated around the fire that the smoke is heading towards them,regardless of where they are seated.

The smoke from a fire is a mixture of gases and small suspendedparticles of soot or other solids, resulting from the burning ofmaterials such as wood. The smoke is a collection of airborne solid andliquid particulates and gases emitted when a material undergoescombustion or pyrolysis, together with the quantity of air that isentrained or otherwise mixed into the mass. Most of the moisture contentremaining in firewood consists of wood resins. As wood heats up in thefire chamber, these resins emit combustible gases which, if somehowignited, can account for as much as half the heat output of the fire.When green or wet firewood is burned, the extra water content turns tosteam and mixes with the wood gases, preventing them from igniting andreleasing their heat value. Conventional fire pits therefore miss halfof their potential heat capability which goes up in the smoke. A hot,more efficient fire actually consumes virtually all of the smokecomponents before they can escape.

Fire pits can vary in complexity from a simple pit in the ground to aportable combustion device. There are commercially available fire pitsconstructed of metals, ranging in size from small portable units tolarge, immobile units. Some of the disadvantages of fire pits are theabove-mentioned ‘following smoke’ effect, as well as the sparks that canfly about in the combustion gases, smoldering logs at the end of a burn,adjustment of the flame and viewing of the flame by all of the peoplegathered around the pit. Portability can be an issue for the largermetal fire pits, leading to rust problems when not taken in out of therain. Portability can also be a factor for hikers, campers, boaters orrecreational vehicle users, where weight or size can be a factor.Cleaning out the units can also be problematic. Larger fire pits requireremoving ash, charcoal and unburned wood. Disposing this can be messyand dangerous. Unless the fire is thoroughly extinguished and the debrisis properly disposed of there is risk of starting a fire. The sparks,smoke and flame height can also create safety issues and potentiallyimpact on the personal health of the gathered people. The fire pit canbe used as a grill for cooking, with the grill either placed above thecombustion as an add-on, or integrated into the structure of the firepit.

Accordingly, it would be desirable to provide a portable combustiondevice that is capable of being used as a stove for cooking and/orheating, which burns commonly available wood and other biomass, andprovides similar heat output as other liquid or gas fuels, that isportable, efficient in its burn and relatively free of smoke and sparks.The combustion device should desirably be easy to carry, low-maintenanceand burn fuel without exhausting significant soot, smoke or toxiccombustion byproducts. Additionally, with complete combustion there arevery few coals and un-combusted wood left at the end of the burn. Thecombustion should desirably employ inexpensive and commerciallyavailable components and conventional construction techniques in itsmanufacture.

SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages of the prior art byproviding a lower and upper forced air system to enhance the combustionprocess. The advantages of having a lower and upper forced air system isapplicable to fire pits of any shape and size. The present inventionprovides a combustion device having a combustion chamber with an openingbetween the interior of the combustion chamber and an ambientenvironment outside of the combustion chamber. The combustion chambercan have at least one lower air jet tube having at least one lower portin communication between an interior of the lower air jet tube and thecombustion chamber where the at least one lower port is in a lowerregion of the combustion chamber. The combustion chamber can also haveat least one upper air jet tube having at least one upper port incommunication between an interior of the upper jet tube and thecombustion chamber, where the at least one upper port is in an upperregion of the combustion chamber. The combustion chamber can also have ablower operatively connected to the air jet tubes, so that when theblower is turned on, air from the blower is forced through the air jettubes, through the ports, and into the combustion chamber.

In an embodiment, the at least one lower port can be within the bottom30% of the combustion chamber. The at least one lower port can compriseat least one port directed upwards and at least one port directeddownwards. The at least one upper port can be within the top half of thecombustion chamber. The combustion device can have a fuel rack, wherethe at least one lower port is lower than the fuel rack. The height ofthe fuel rack can be adjustable. At least one upper port can be higherthan the fuel rack. The combustion chamber can have a plurality ofperforations between the interior of the combustion chamber and theambient environment outside of the combustion chamber. The combustiondevice can have a manifold in fluid communication between the blower andthe jet tubes, so that when the blower is turned on, air from the bloweris forced through the air jet tubes, through the ports, and into thecombustion chamber. The combustion device can have a grill surface atleast partially over the opening between the interior of the combustionchamber and the ambient environment outside of the combustion chamber.The grill surface can slide on a track between a first position over theopening and a second position that exposes at least a portion of theopening, so that new fuel can be added to the combustion device withoutremoving the grill surface from the combustion device. The combustiondevice can have a detachable power module and a rechargeable batterywithin the detachable power module, wherein the rechargeable battery canbe selectively connected to the blower to provide power to the blower.The blower can be within the detachable power module, wherein the blowercan be selectively connectable to the manifold. At least one upper jettube can be located along sidewalls of the combustion chamber. Thecombustion device can have a slidable ash door in the bottom of thecombustion chamber, the slidable ash door can be adapted for a user tograsp and slide the slidable ash door open while a fire is burning inthe combustion device. The combustion device can have at least onehandle, where the at least one handle is adapted for a user to grasp theat least one handle and move the combustion device by hand while a fireis burning in the combustion device. The flow rate of air from theblower into the combustion chamber can be controllable by adjusting thespeed of the blower. The speed of the blower can be adjustable through awireless connection. The flow rate of air from the blower into at leastone jet tube can be controllable by adjusting a baffle between themanifold and the at least one jet tube.

A method for smokeless combustion includes actuating a fan motor that isattached to a blower; drawing ambient air from the exterior of thecombustion device; propelling the ambient air through the blower andinto a manifold; forcing the propelled air into at least one of a lowerjet tube or a upper jet tube; forcing the propelled air within the atleast one jet tube along the body of the jet tube and out a port; andforcing a sufficient quantity of air at a sufficient rate to causecomplete combustion of the fuel and exhaust gases such that the quantityof emitted smoke is reduced toward a zero value.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention description below refers to the accompanying drawings, ofwhich:

FIG. 1 is a perspective view of a smokeless fire pit, according to anillustrative embodiment;

FIG. 2 is a perspective view of the smokeless fire pit, according to theillustrative embodiment;

FIG. 3 is a view of a first end of the smokeless fire pit with amanifold, according to the illustrative embodiment;

FIG. 4 is a view of a second end of the smokeless fire pit, according tothe illustrative embodiment;

FIG. 5 is a top view of the smokeless fire pit, according to theillustrative embodiment;

FIG. 6 is a bottom view of the smokeless fire pit, according to theillustrative embodiment;

FIG. 7 is a side view of the smokeless fire pit, according to theillustrative embodiment;

FIG. 8 is a cross-sectional view of the smokeless fire pit along lines8-8 of FIG. 1, according to the illustrative embodiment;

FIG. 9 is a cross-sectional view of the smokeless fire pit along lines9-9 of FIG. 5, according to the illustrative embodiment;

FIG. 10 is a perspective schematic view of the smokeless fire pit,according to the illustrative embodiment;

FIG. 11 is a view of the smokeless fire pit showing the grill assemblypartially removed, according to the illustrative embodiment;

FIG. 12 is a view of the smokeless fire pit showing the power moduleremoved, according to the illustrative embodiment;

FIG. 13A is a view of a locking mechanism for the power module showingthe power module being removed, according to the illustrativeembodiment;

FIG. 13B is a view of a locking mechanism for the power module showingthe power module being re-engaged with the smokeless fire pit, accordingto the illustrative embodiment;

FIG. 14 is an exploded view of a body housing for the smokeless firepit, according to the illustrative embodiment;

FIG. 15 is an exploded view of a manifold for the smokeless fire pit,according to the illustrative embodiment;

FIG. 16 is an exploded view of the power module for the smokeless firepit, according to the illustrative embodiment;

FIG. 17 is an exploded view of a housing for the power module for thesmokeless fire pit, according to the illustrative embodiment;

FIG. 18 is an exploded view of a blower fan components for the smokelessfire pit, according to the illustrative embodiment; and

FIG. 19 is an exploded view of the blower body for the smokeless firepit, according to the illustrative embodiment.

DETAILED DESCRIPTION

A smokeless “fire pit” (as defined herein) is a compact and portablecombustion device that can use a forced air mechanism to burn fuel morecleanly with brighter illumination, more efficient heating and withoutthe inconvenience of smoke from the fire following people located aroundthe fire pit. A group of people can comfortably sit in a full circlearound the combustion device, which can have an edge at (approximately)waist level when seated, and experience an open fire without (free of)the inconvenience of smoke from the fire following people around becausea forced air mechanism encourages a more complete combustion of thefuel, leaving little smoke. With the forced air, the fire burns cleaner,hotter and provides a brighter illumination. The variable speed of thefan and forced air also allows a user to control the rate of combustion.An illustrative fire pit 100 is shown in FIG. 1, according to anembodiment. The overall weight of the fire pit 100 is about 18 pounds,according to an illustrative (exemplary) embodiment. The relativelylight weight and overall compact size provides a fire pit that can becarried to a beach, where there can be fire use restrictions or limitedfuel availability. The compact size can be convenient for confinedpatios and backyards. The fire pit can be carried while a fire is litwithin the fire pit, providing for relocation during use, where largerfixed fire pits cannot be so moved. The portability of the fire pit canalso allow the fire pit to be stored indoors, in a house, shed, garage,or other out building, thereby avoiding environmentally-induceddeterioration via rust and corrosion.

The illustrative fire pit 100 is a combustion device that can burn atleast one of wood, coals, compressed wood logs or bricquettes as fuel.The fire pit 100 is sized to accommodate cord wood in the size range ofup to approximately 16 inches long, without the need for further cuttingor splitting of the logs. The controlled air flow system provides for acontrolled burn of a longer time and greater efficiency, as will be morefully described below. The air flow from the impeller fan, (hereinaftercalled a “blower”) through a manifold into the combustion chamber can becontrollable by at least one of increasing or decreasing the speed ofthe blower such that the combustion consumes at least a portion of theexhaust gases that create smoke, flame size and combustion rate. In anembodiment, the illustrative blower is a radial fan. In anotherembodiment, the blower can be an axial fan. The fire pit 100 can includethe opening 110 for the fire pit, a grill top assembly 120 that coversthe opening 110, a body housing 130 that encloses a combustion chamberthat can include a fuel source on an adjustable fuel rack, side walls,end caps and/or at least one of a plurality of legs 180. The fire pit100 can also include at least one lower air jet tube and at least oneupper air jet tube. The jet tubes can extend from a manifold to receiveforced air from the manifold and into the combustion chamber that can besituated above a base plate 140. A power module 160 can include abattery pack, an air blower that can be a radial impeller fan, and thatcan be constructed and arranged to drive air from an ambient source intoa manifold or directly into the jet tubes, a fan motor, fan motorcontrols. A primary and secondary forced air system enhances thecombustion process and is applicable to fire pits of any shape and size.

In an illustrative embodiment, the grill top assembly 120 is a unit thatcan move laterally onto and off or can be cantilevered from the top offire pit 100, as described more fully below. The grill top can slidelaterally in a track or groove so that it can be entirely removed,and/or at least partially removed to allow for the addition of new fuelwhile still retaining partially cooked foods on the flat grill top. Thiscan allow new fuel to be added into the combustion chamber without auser needing to entirely remove the grill top and any food on the grilltop. In alternate embodiments, the grill top can be lifted verticallyoff of the combustion device, can have hinge pins that allow the grilltop assembly to hinge away from the combustion device and/or slidelaterally out of the hinge mechanism, or other possible mechanisms. Thegrill top assembly 120 can include a support rail 122 that is attachedto a spark arrestor 124, which can be a wire mesh screen for reducingthe presence of sparks in the combustion gases emanating from the firepit during combustion. In the illustrative embodiment, the sparkarrestor 124 is shown as also being the grilling surface, however thespark arrestor 124 can be separate from, and below the grilling surface.The support rail 122 also functions to prevent any foods placed onto thegrill top from sliding off the grill during cooking. The shape of thegrill top assembly 120 and the body housing 130 are rectilinear. Inother embodiments, it is contemplated that they can have another shape(for example, a circular or ovoid profile). The illustrative supportrail 122 is likewise rectilinear, and is supported by vertical supports126 that are attached to the perimeter support 128. The perimetersupport 128 and the support rail 122 can be sized to the same dimensionsand can be formed of wire of a similar gauge. The perimeter support 128,support rail 122 and vertical supports can be connected and joined by awelding mechanism. The wire mesh of the spark arrestor 124 can be of alighter gauge wire than the support rail, and can be formed with awelding process to form a unitary structure with the perimeter support128, support rail 122 and vertical supports 126. Handles 131 can beattached to the body housing 130 at either end and can be counter posed.In an embodiment, a combustion device has at least one handle attachedto an end cap for carrying and positioning the combustion device.Handles 131 are constructed and arranged to support the weight of thefire pit during movement.

The side panels 132 of the body housing 130 are perforated with at leastone hole in its material. The perforated metal sides of the fire pit 100facilitate several functions. First, the perforated metal sides 132control air flow. They benefit the efficiency of the combustion processby providing introduction of air from the ambient air, not only when thefan is running but for passive operation should the fan lose power orthe user prefer not to use the blower fan of attached the power module160. Ambient air can come from the ambient environment outdoors wherethe combustion device can be used. The power module 160 can include acontrol interface linked to a control unit for actuating and managing ablower fan to create a flow of air in the fire pit, and batteries formaintaining that air flow. In other embodiments, the control unit canadjust one or more adjustable baffles and regulate air flow into thecombustion chamber. The control unit can include a central processor andcan be programmable and/or pre-programmed. The power module can bedirectly controllable, and/or can be controllable remotely by at leastone Bluetooth® device, a cellular phone or programmable computingdevice. The power module 160 can be attachable and detachable. By way ofnon-limiting example, the power module can be attached and detached byaction of a button that causes engaging locking arms to inter-engagewith brackets mounted on the manifold 150 (as will be described morefully below). The perforated metal sides 132 can be “tuned” to aspecific hole opening size so that wind doesn't interfere with thecontrolled combustion air flow from the lower and upper jets. In anembodiment, a perforation hole has a diameter of approximately 1 mm andthe holes are spaced approximately 1 mm apart. It is contemplated thatin further embodiments, the holes can be larger or smaller (for example,0.75 mm or 1.5 mm), and either situated closer or farther apart. Theperforated sides 132 keep sparks in but allow the flame to be observed.The shape of the sides, which can be extruded, also encourages efficientcombustion. Most importantly, while lit at night, the perforated sidesseem to “disappear”, allowing for a better viewing experience. As usedherein the directional terms, such as, but not limited to, “up” and“down”, “upward” and “downward”, “rear”, “rearward” and “forward”, “top”and “bottom”, “inside” and “outer”, “front” and “back”, “inner” and“outer”, “interior” and “exterior”, “downward” and “upward”,“horizontal” and “vertical” should be taken as relative conventionsonly, rather than absolute indications of orientation or direction withrespect to the acting direction of the force of gravity.

The power module 160 can be positioned at one end of the body housing130 and will be more fully described below. The power module 160controls a blower fan that provides a flow of air into the interior ofthe body housing 130 for control and sustainment of the combustionprocess by a multiplicity of air jets (explained more fully below). Thebody housing can be sized such that it has enough capacity to hold up tothree conventionally sized pieces of cordwood. Fuel can be inserted atthe top of the body housing by sliding back the grill top assembly (ifit is in use) and lit conventionally by using kindling or inserting fuelonto the embers after the initial wood has burned down. The body housingcan be constructed of materials, such as steel alloys, aluminum andaluminum alloys, titanium, ceramics, or any other material (orcombination of materials) that is durable and capable of with standinghigh temperatures. The size of the flame can be controlled by adjustingthe blower fan speed and/or by adjusting at least one baffle between themanifold and at least one jet tube, explained more fully below.Adjusting the fan speed can be accomplished remotely, using a Bluetooth®wireless communication link, or another remote communications system,with a receiver built into the power module. Bluetooth® is a wirelesstechnology standard for exchanging data over short distances. TheBluetooth® feature can be embedded in the power module control so aperson can control the fan speed remotely through a smartphone or other(e.g. handheld) device (e.g. a tablet, laptop, etc.) as well asmonitoring battery capacity and the lifespan of the current batterycharge. The implementation of an application on a remote device thatcommunicates via an embedded wireless communication protocol and allowscontrol and monitoring of the power module 160 should be clear to thoseof skill in the art. Likewise, the arrangement of monitoring (e.g.temperature) and control (e.g. fan speed) devices within the powermodule should be clear to those of skill, as well as their interfacewith a commercially available wireless (e.g. Bluetooth®) communicationmodule.

The power module can include a button, knob, or other interface tocontrol blower fan speeds and a user interface that provides fan speedinformation as well as battery charge capacity, either with a smallscreen or an array of LEDs. A USB charge out feature can be provided torecharge cell phone batteries or to run peripheral accessories. A methodfor a smokeless combustion device can include actuating a fan motor thatis attached to a blower such as an axial or radial impeller fan; drawingambient air from the exterior of the combustion device; propelling theambient air through the impeller fan and into a manifold; forcing thepropelled air into at least one of a lower jet tube or a upper jet tube;forcing the propelled air within the jet tubes along the body of the jettube and out a port; transmitting the propelled air exiting the jet tubetowards the combustion fire; and forcing a sufficient quantity of air ata sufficient rate to cause complete combustion of the fuel and exhaustgases such that the quantity of emitted smoke is reduced toward a zerovalue.

FIG. 2 is a perspective view of the smokeless fire pit with the grilltop removed, according to the illustrative embodiment. The body housingcan have a length OL1 of approximately 22 inches (±2 inches) and canhave a height OH1 of approximately 9.5 inches (±2 inches). In anembodiment, a fire pit 100 is provided with a primary (“lower”) jet 210and two secondary (“upper”) jets 200. Each of the lower and upper jetscan have a plurality of ports 202 that are sized and dimensioned toprovide for an air flow from the interior of each jet into thecombustion chamber 134. Air can be transmitted from the jet tubesthrough the ports and into the combustion chamber. A lower jet tube 210is a tube with an opening at one end for receiving forced air from theblower, and a plurality of ports 202 for passing forced air into thecombustion chamber. The lower jet tube 210 can have at least one port202 oriented downwards toward the base plate to reduce the coals, andcan have at least one port 202 oriented upwards towards the fuel. Anupper jet tube 200 is a tube with an opening at one end for receivingforced air from the blower, and a plurality of ports 202 for passingforced air into the combustion chamber. For the purposes of describingthis embodiment, each of the illustrative jet tubes can be a hollow tubethat is open at one end (the end nearest the manifold 150) and isprovided with a plurality of air ports 202, for the movement of air fromthe manifold 150 into the combustion chamber 134. In the presentembodiment the jet tubes are depicted as being within the combustionchamber, however at least one jet tube can be located outside of thecombustion chamber, and the forced air can be transmitted through theports 202 into the combustion chamber. A manifold 150 can be constructedand arranged to receive forced air from a blower (not shown) with ablower motor that is activated by the power module 160. The manifold candistribute the forced air into the respective jet tubes, to drive airinto the combustion chamber. The power module 160 can be provided with acontrol button 162. A perforated end cap 136 for viewing and aiding incombustion can be situated at an end of the body housing 130, counterposed to the power module. Legs 180 can be connected to the base plate140 of the body housing 130 at each of the four corners at a mountingsupport 182 that can be attached to the base plate 140 by welded, rivetsor another attachment mechanism. The mounting supports 182 can beconstructed and arranged with a plurality of detent holes 184 and detentbuttons to allow the legs to fold from an extended configuration tofolded configuration, and folded to extended configurations. By way ofnon-limiting example, the mounting supports 182 can be constructed withthree detent holes 184. At least one lockable leg can be folded from anextended configuration to a folded configuration and back to an extendedconfiguration. A pivot pin 186 is located at one end of each leg. Theextended configuration can be defined as the legs being locked into aposition such that the length of each leg is nearly perpendicular to anaxis ABP drawn along the length of the base plate 140 or bottom of thebody housing 130. The folded configuration can be defined as the legsbeing folded such that each leg is in proximity to the base plate 140 orbottom of the body housing 130. A base plate 140 can be constructed ofform sheet steel. In the extended configuration, the legs support thefire pit 100 such that the body of the smokeless firepit is situatedabove the ground and there is a space between the bottom of the bodyhousing 130 and the supporting ground. In the folded configuration, thebase plate 140 rests on the supporting ground.

FIG. 3 is a view of a first end of the smokeless fire pit with amanifold, according to the illustrative embodiment. The fire pit 100 canhave a width of approximately 12 inches (±2 inches). A door for removalof ash from the combustion chamber is located along the base plate 140,or bottom of the body housing. The ash door handle 300 for opening andclosing the ash door is shown. The detent button 188 on each of the legs180 is also shown. The profile of the body housing 130 taken across itswidth can be an irregular polygonal shape. The grill top assembly 120and the base plate 140 can have a similar width. The body housing can bewider along the sides 132 and can vary such that a fold 133 along eachside 132 can be wider than either of the base plate 140 and/or the grilltop assembly 120. This greater width can correspond to the location ofthe upper jet tubes 200. The bottom of the body housing 130 can benarrower than the side 132 at folds 133 so that ash and combustionmaterials tend to settle toward the bottom (base plate 140). Inwardsloping sides 132 urge the ash materials towards the ash door.

FIG. 4 is a view of the fire pit, showing the end that is opposite theend with the power module 160 of FIG. 3. An end cap 136 can beconstructed with a perforated panel 402 that is perforated with at leastone hole 403 and can function as the perforated sides 132, alreadydescribed above.

A top view of the fire pit is shown in FIG. 5. The grill top assembly120 can be narrower than the sides 132 at the folds 133 and not lowerthan the end cap 136 and the manifold 150.

FIG. 6 is a bottom view of the fire pit. By way of non-limiting example,the ash door 600 is shown as closer to the end cap 136 than top themanifold 150. To dump the ash, the handle 300 of the ash door can beactuated and the ash door 600 is opened by grasping the handle andpulling the door in its slide tracks back from the body housing. Thedoor can be secured with a latch mechanism of various types, includingbut not limited to a cam lock, a slam lock, a spring latch, acompression latch, a draw latch, a rotary latch and a bolt lock latch.The accumulated ash in proximity to the ash door is then dumped throughthe opening 602 in the base plate 140 that is covered by the ash door600. Ash closer to the power module 160 can be dumped by raising the endin proximity of the power module 160 by raising a handle 110 (not shown)at the end opposite of the end cap 136. Ash then falls downwards and outof the opening 602. With regard to the legs 180, a folded spring 610 canprovide the locking force for the detent 180 that holds the legs in theextended configuration.

FIG. 7 is a side view the fire pit. As shown that the ash door can beopened to position 600′ to facilitate the removal of ash.

FIG. 8 is a cross sectional view of the smokeless fire pit along lines8-8 of FIG. 1. The exemplary combustion chamber 134 can include at leastone lower jet tube 210 located along the bottom of the combustionchamber, either on the inside or the outside of the combustion chamber.The ports 202 from the lower jet tube 210 can be within the bottom 30%of the combustion chamber. The ports 202 from the lower jet tube 210 canbe within the bottom 25% of the combustion chamber. The ports 202 fromthe lower jet tube 210 can be within the bottom 20% of the combustionchamber. The ports 202 from the lower jet tube 210 can be above thebottom 5% of the combustion chamber. At least a portion of the ports 202from the lower jet tube 210 can be above the bottom 10% of thecombustion chamber.

The combustion chamber 134 can include at least one jet tube 200 thatcan be mounted along the outside or inside of the combustion chamber.There can be at least two upper jet tubes 200 that can be mounted onealong each of the side walls, for a more complete combustion of thesmoke gases. The ports 202 from the at least one upper jet tube 200 canbe in the top 50% of the combustion chamber. The ports 202 from the atleast one upper jet tube 200 can be in the top 40% of the combustionchamber. The ports 202 from the at least one upper jet tube 200 can bein the top 30% of the combustion chamber. The ports 202 from the atleast one upper jet tube 200 can be in the top 25% of the combustionchamber. The ports 202 from the at least one upper jet tube can be belowthe top 10% of the combustion chamber. The ports 202 from the at leastone upper jet tube 200 can be below the top 15% of the combustionchamber. The ports 202 from the at least one upper jet tube 200 can bebelow the top 20% of the combustion chamber.

The legs 180 are shown with greater detail of the folded leaf springs610 supporting the locking detents 188. The air flow is depicted fromthe lower jet 210 and upper jets 200 through a multiplicity of variousperforated holes 202 to introduce forced air to surround the combustionchamber 134. A blower can draw air from the outside and can force airinto a manifold connected to the lower and upper jet tubes. The blowercan be an axial impeller fan, traditional bladed fan, or other blowersas are known in the art. The lower jet tube 210 can be positionedunderneath the fuel rack assembly 800 that rests on the bottom of thebody housing 130. This lower jet can force air at multiple anglesbeneath the burning log to encourage even combustion to create a hotterand cleaner flame. Air can be forced directly downwards, directlyupwards, upwards and/or downwards at different angles, or combinationsof multiple different directions. As shown in the illustrativeembodiment, air can be forced directly downwards and can be forcedupwards at three different angles, although other arrangements andnumbers of angles are specifically contemplated. By way of non-limitingexample, air can be forced upwards at angles in a range from 0-45degrees from directly vertical (relative to a vertical axis extendingfrom the center of the earth through the center of the base plate andupwards, through the center or the top opening). In an embodiment, anangular orientation of 45 degrees creates a more efficacious combustion.In a further embodiment with a greater number of jets (for example, fouror five jets), other angular orientations may be used for greaterefficiency of combustion. It is further contemplated that theorientation of the jets can be adjusted, either manually orautomatically. Changes in the position of the internal fuel rackassembly that supports the combustion material (described more fullybelow) can result in a re-direction of the jets to a new angularorientation. The position of the lower jet tube 210 at the bottom canalso allow the user to place a new log onto the coal bed and almostinstantaneously ignite the new log to create a full flame. Doing so witha conventional fire pit would not ignite the added log and createsexcessive smoke, with a loss of up to half the potential heat energy,lost in that smoke.

As shown in FIG. 8, the lower jet can include air ports directeddownward towards the coal bed to fully combust these coals, therebyreducing the coals to ash. This provides for a long burn time with manylogs added in an evening without having to empty the fire pit of ash andcoals. This provides for a hotter combustion, which not only pleases theusers, but also consumes more of the resins and energy in the smoke,thereby abating the amount of smoke and smoky exhaust. At the end of theburn, the sliding ash door 600 can be slid open and the ash can besafely disposed of Upper jet tubes 200 can receive air from the blowerand can be positioned opposing each other at upper sides of thecombustion chamber 134, situated above the top of the logs with airports tuned to allow air penetration into the flames themselves, tocomplete the combustion. Any smoke that is not ignited by the lowerjet(s) is then ignited as a result of the airflow from the upper jets.

An internal rack assembly 800 can be a device that holds the combustionfuel above the lower jet 200. By way of non-limiting example, the fuelrack assembly 800 can be provided with two end handles 802 that areconnected to a matrix of bent cross spars 804 that are joined with eachother by welded bottom rods 806 and end rods 808. The fuel rack locatedin the combustion chamber can be raised or lowered. The rack assembly800 can rest on folded linear bottom rods 810. The rack assembly 800 canbe removable from the fire pit 100 by manipulation and removal throughthe opening covered by the grill top assembly 120. The height of thefuel rack assembly 800 can be adjustable. In the embodiment of FIG. 8,the rack assembly 800 can be raised to a secondary height when thehandles 802 are engaged with brackets 1508 (described more fully below)so that when charcoal is burned or the coal bed is low, it can be raisedinto proximity with the food on the grill. The height of the fuel rackcould also be adjustable by way of chains and sprockets, scissor jacks,or other means known in the art. The grill top 124 can be a sparkarrestor and can support items of food. The jets inject a supply of airinto the combustion chamber for an even, controlled burning of thefuels. The even placement of the air ports in the jets burns the fuelevenly, avoiding a smoldering chunk at the end of the burn.

FIG. 9 is a cross-sectional view of the smokeless fire pit along lines9-9 of FIG. 5. Power module 160 can have a battery pack 900. There canbe enough battery capacity to run the FP for up to 40 hours on the lowfan setting in an embodiment. It is contemplated that larger capacitybatteries or more batteries could be provided for a longer charge life.In an embodiment, the batteries are fixed within the removable powermodule and the power module can be removed and recharged. Therechargeable batteries can be taken indoors or to a vehicle to berecharged through a micro USB port. In the illustrative embodiment, thebatteries are fixed within the power module and are non-removable. Inother embodiments, the batteries can be arranged in a removable pack.Likewise, the power module itself is removable for recharging of thebatteries. It is contemplated that the power module and forced airsystem can be charged and run while connected to a charging cable thatis plugged into conventional household current. In another embodiment,the forced air system can directly wired into a stationary power sourcewhen a larger and immobile combustion device is installed.

Furthermore, if external devices are attached at a receptacle plug suchas a USB port to the power module, they can be recharged from the chargein the battery pack. The folds of the bottom rods 810 are shown. Theupper jets 200 and the lower jet 210 can be joined to the manifold andholes 902 that perforate the inner manifold 1506 to allow air to movefrom inside the manifold 150 into the jets 200, 210.

FIG. 10 is a perspective schematic view of the smokeless fire pit,according to an illustrative embodiment. FIG. 10 shows a flow of airfrom a blower fan assembly 1000 through the blower body 1002 into themanifold 150, and into the lower jet 210 and the upper jets 200. Ambientair enters into the blower fan 1000 via an intake 1004 located at oneend of the power module 160. The air is then propelled through theblower body by movement of the blower fan. The air can then be forcedinto the manifold 150. The forced air encounters the manifold radiationshield 1504 that is placed so as to admit the forced air from the blowerbody 1002 without causing impedance to the air flow, while at the sametime preventing heat from the combustion chamber from entering the powermodule 160. This can be one of two preventive features to keep the powermodule 160 from overheating as a result of combustion. The secondpreventive feature is an air space 1020 that is created between themanifold 150 and the power module 160. In a further embodiment, a baffle1003 can be placed along the path of the air flow at a point between ajet and the blower body, so that when the baffle is activated, it canrotate from a position where it is not impeding the air flow to aposition where it is partially or fully impeding the air flow, so as toregulate the amount of air flowing into a particular jet. It iscontemplated that each of the jet tubes can be provided with a baffle,and that the baffles can be adjusted individually and/or collectively,either manually or collectively.

FIG. 11 shows the lateral movement of the grill top assembly 120 ontoand off of the body housing 130 over the end cap 136. This movementpermits the re-fueling the combustion chamber, as well as removal of thegrill top, if desired.

FIG. 12 depicts the removable power module 160 that is detachable fromthe body housing 130 at the manifold 150. A shroud 1021 for the blowerbody 1002 remains attached to the manifold 150.

FIGS. 13A and 13B show the locking mechanism for attachment of, anddetachment of the power module 160 to the manifold 150, according to anembodiment. A button 1302 can actuates locking arm 1304 that engages atab 1306 located on the manifold 150. The locking arm 1304 is kept undertension by a spring 1308 that is wrapped around an axle 1310 and thatengages the inner surface of a fold 1312 on the top of the locking arm1304. FIG. 13A is a view of a locking mechanism for the power moduleshowing the power module being removed. A downward force in direction1320 is applied to the button 1302 that moves the locking arm 1304against the tension of spring 1308, allowing the end of the locking arm1304 to pass beneath and inside of tab 1306. FIG. 13B is a view of alocking mechanism for the power module showing the power module beingre-engaged with the smokeless fire pit. When the downward force isremoved from the button 1302, the tension of spring 1308 pushes lockingarm 1304 upwards, thereby locking the power module 160 to the manifold.The attachment is sustained by the constant tension of spring 1308.

The exploded view of FIG. 14 shows the components and assemblies as setforth above. The power module is not shown as attached to the manifold150. As shown, the components can be formed of sheet metals, wire,extruded parts, and/or other methods of manufacture, which are formedand joined into various assemblies. This construction keeps the weightrelatively light.

In FIG. 15, the various components of the manifold are shown in anexploded view, according to an embodiment. The manifold 150 is anassembly that can include a handle 110, an outer manifold 1500 and aninner manifold 1506. The outer manifold has a manifold inlet 1502 toguide the air into the manifold 150. A radiation shield 1504 protectsthe manifold inlet 1502 from radiant heat from the combustion chamberthat might otherwise enter the power module and cause failure of thepower module. The inner manifold 1506 is provided with openings 902 forthe movement of air into the jets. A bracket 1508 for holding the rackassembly 800, with attaching screw 1510, is shown in proximity to theinner manifold 1506. Tabs 1306 and the center manifold bracket 1512 areshown in proximity to the outer manifold 1500.

FIG. 16 is an exploded view of the power module 160 for the smokelessfire pit, showing the components according to an embodiment. A housingback 1602 is the portion that connects to the manifold. The blower fan1000 includes a blower body 1002, a blower fan with motor 1606,batteries 900 and is protected by a housing front 1604. Not shown arethe electrical components that turn the blower fan on and off, andregulate its rate of flow.

The sub-components of the housing back 1602 are shown in FIG. 17,according to an embodiment. The components include a set of bottombrackets 1702, a latch stand off 1704 and a duct gasket 1706. Aplurality of screws hold the brackets 1702 and stand off 1704 to thehousing back 1602.

The blower fan components are shown in FIG. 18 is an exploded view,according to an embodiment. The blower fan and motor 1606 can becomprised of a motor 1802 and an impeller 1804. The motor is acommercially available fan motor. The manifold is constructed andarranged to include a manifold heat radiation shield 1806 thatdissipates excessive heat within the power module, while an insulationshield 1808 protects the on/off control components from excessive heat.Various screws 1810 anchor the components to one another.

FIG. 19 is an exploded view of the blower body 1602, according to anembodiment. The components include the button 1302 that releases thepower module from the manifold. Latch 1304 with the fold 1312, thetension springs 1308 and the axle 1310 are shown. Tensions spring 1308can be a torsion spring.

It should be clear from the foregoing that the illustrative fire pit isa combustion device that draws ambient air into an impeller fan thatpropels the forced air into a manifold and drives that air into jettubes. The forced air then exits the jet tubes through ports and isdirected into the combustion chamber. The forcing of air into thecombustion chamber during combustion causes a more efficient burning andconsumption of the fuel. This in turn consumes most, if not all of thesmoke and fully consumes the fuel to avoid smoldering fuel components.Perforations in the side walls and end caps contribute to both the drawof air into the combustion chamber, but also provide a viewing of thecombustion. The airflow is controllable by operation of the powermodule. The combustion device is compact, built of light materials andis readily portable.

The foregoing has been a detailed description of illustrativeembodiments of the invention. Various modifications and additions can bemade without departing from the spirit and scope of this invention.Features of each of the various embodiments described above may becombined with features of other described embodiments as appropriate inorder to provide a multiplicity of feature combinations in associatednew embodiments. Furthermore, while the foregoing describes a number ofseparate embodiments of the apparatus and method of the presentinvention, what has been described herein is merely illustrative of theapplication of the principles of the present invention. For example,while the current embodiment does not use a Thermo-electric Generator(TEG) to generate the power for the fan or a charge out feature, it iscontemplated that in another embodiment, a TEG can be included in ornear the combustion chamber for the generation of electrical powerduring combustion. While in the present embodiment, a single blower fanis shown, it is expressly contemplated that more than one blower fancould be provided. It is further contemplated that each of the lower jetand upper jets can have their own blower fan, acting jointly orindependently. The size and shape of the body housing can include othershapes, for example, ovoid hexagonal, round in profile. The size of thefire pit can be larger, and the above described features can be providedas a permanently situated installation, for example, in a fire place orin a fire box. It is contemplated that the jet tubes can be mountedoutside the combustion chamber, and ported into the combustion chamber.It is further contemplated that the air induction system can be arrangedwithout a manifold and that a blower (or a plurality of blowers) can bedirectly immediately into each jet. Furthermore, the above describedfeatures (in particular, the forced air system, including the lower andupper forced air systems) can be provided as part of a kit forinstallation in a custom designed fire pit. Additionally, while the airflow driver is defined herein as an impeller, it is expresslycontemplated that a storage tank or air compressor could be used forrelease at appropriate time, in appropriate volume via a valve andconduit. Accordingly, this description is meant to be taken only by wayof example, and not to otherwise limit the scope of this invention.

What is claimed is:
 1. A combustion device comprising: a combustionchamber having an opening between an interior of the combustion chamberand an ambient environment outside of the combustion chamber; at leastone lower air jet tube having at least one lower port in communicationbetween an interior of the lower air jet tube and the combustionchamber, the at least one lower port being in a lower region of thecombustion chamber; at least one upper air jet tube having at least oneupper port in communication between an interior of the upper jet tubeand the combustion chamber, the at least one upper port being in anupper region of the combustion chamber; a blower operatively connectedto the air jet tubes, whereby when the blower is turned on, air from theblower is forced through the air jet tubes, through the ports, and intothe combustion chamber; and a grill surface at least partially over theopening between the interior of the combustion chamber and the ambientenvironment outside of the combustion chamber.
 2. The combustion deviceof claim 1, wherein the at least one lower port is within the bottom 30%of the combustion chamber.
 3. The combustion device of claim 2, whereinthe at least one lower port comprises at least one port directed upwardsand at least one port directed downwards.
 4. The combustion device ofclaim 1, wherein the at least one upper port is within the top half ofthe combustion chamber.
 5. The combustion device of claim 1, wherein theheight of the fuel rack is adjustable.
 6. The combustion device of claim1, wherein the at least one upper port is higher than the fuel rack. 7.The combustion device of claim 1, wherein the grill surface can slide ona track between a first position over the opening and a second positionthat exposes at least a portion of the opening, whereby new fuel can beadded to the combustion device without removing the grill surface fromthe combustion device.
 8. The combustion device of claim 1, wherein theat least one upper jet tubes are located along sidewalls of thecombustion chamber.
 9. The combustion device of claim 1, furthercomprising a slidable ash door in the bottom of the combustion chamber,the slidable ash door adapted for a user to grasp and slide the slidableash door open while a fire is burning in the combustion device.
 10. Thecombustion device of claim 1, further comprising a fuel rack, whereinthe at least one lower port is lower than the fuel rack.
 11. Acombustion device comprising: a combustion chamber having an openingbetween an interior of the combustion chamber and an ambient environmentoutside of the combustion chamber; at least one lower air jet tubehaving at least one lower port in communication between an interior ofthe lower air jet tube and the combustion chamber, the at least onelower port being in a lower region of the combustion chamber; at leastone upper air jet tube having at least one upper port in communicationbetween an interior of the upper jet tube and the combustion chamber,the at least one upper port being in an upper region of the combustionchamber; a blower operatively connected to the air jet tubes, wherebywhen the blower is turned on, air from the blower is forced through theair jet tubes, through the ports, and into the combustion chamber; amanifold in fluid communication between the blower and the jet tubes,whereby when the blower is on, air from the blower is forced through themanifold, through the jet tubes, through the ports, and into thecombustion chamber; and a detachable power module and a rechargeablebattery within the detachable power module, the rechargeable batterybeing selectively connectable to the blower to provide power to theblower.
 12. The combustion device of claim 11, wherein the blower iswithin the detachable power module, the blower being selectivelyconnectable to the manifold.
 13. A combustion device comprising: acombustion chamber having an opening between an interior of thecombustion chamber and an ambient environment outside of the combustionchamber; at least one lower air jet tube having at least one lower portin communication between an interior of the lower air jet tube and thecombustion chamber, the at least one lower port being in a lower regionof the combustion chamber; at least one upper air jet tube having atleast one upper port in communication between an interior of the upperjet tube and the combustion chamber, the at least one upper port beingin an upper region of the combustion chamber; and a blower operativelyconnected to the air jet tubes, whereby when the blower is turned on,air from the blower is forced through the air jet tubes, through theports, and into the combustion chamber, wherein a flow rate of air fromthe blower into the combustion chamber is controllable by adjusting thespeed of the blower, and wherein the speed of the blower is adjustablethrough a wireless connection.
 14. A combustion device comprising: acombustion chamber having an opening between an interior of thecombustion chamber and an ambient environment outside of the combustionchamber; at least one lower air jet tube having at least one lower portin communication between an interior of the lower air jet tube and thecombustion chamber, the at least one lower port being in a lower regionof the combustion chamber; at least one upper air jet tube having atleast one upper port in communication between an interior of the upperjet tube and the combustion chamber, the at least one upper port beingin an upper region of the combustion chamber; a blower operativelyconnected to the air jet tubes, whereby when the blower is turned on,air from the blower is forced through the air jet tubes, through theports, and into the combustion chamber; and a manifold in fluidcommunication between the blower and the jet tubes, whereby when theblower is on, air from the blower is forced through the manifold,through the jet tubes, through the ports, and into the combustionchamber, wherein the flow rate of air from the blower into at least onejet tube is controllable by adjusting a baffle between the manifold andthe at least one jet tube.